A conveying system incorporating one or more carrier chains is commonly used to transport cartons through a packaging machine by which the cartons are erected, loaded, and sealed. Each carrier chain is typically tightened around two sprockets that are spaced apart. The links of the carrier chain engage the teeth of the sprockets and the sprockets rotate to drive the carrier chain. In some applications, a guide track, having surfaces above and below the chain, constrains the movement of the chain to a nearly linear path as the chain moves between the sprockets. The amount of play between the guide track and the chain determines how much the individual links of the chain can rotate or otherwise deviate from the linear path.
A typical carrier chain is a roller chain that includes several different types of links including pin links, roller links, and attachment links. The attachment links are spaced along each roller chain at a regular interval and a support member, such as a lug, is integral or attached to the attachment link.
Each support member supports and abuts a portion of a carton that has been at least partially erected, and cooperates with other support members to transport the carton through a packaging machine where the carton is loaded with articles and folded and secured to form a package. The support members support the carton to keep the corners of the carton substantially square before and during loading and as the end flaps of the carton are closed and glued. The support members can transport the package through the packaging machine by pushing or otherwise causing the package to slide along a flat supporting surface (such as a dead plate or otherwise any stationary support member) of the conveyor. Or the supporting surface can be defined by conveyor plates which are attached to the carrier chains or otherwise are not stationary. As the package slides along the supporting surface of the conveyor, the support members are subjected to numerous opposing forces, such as the frictional forces between the package and the supporting surface, package guides, and flap folding mechanisms, and the forces caused by any change in momentum and/or compression of the package. These opposing forces cause the attachment link to rotate, to the extent allowed by the guide track, and causes the support member to angularly displace relative to a plane that is perpendicular to the support surface or tilt according to the degree of rotation of the attachment link. The play between the guide track and the rollers of the carrier chain allow the attachment link a certain degree of rotation. A large amount of tilt of the support members can cause problems as or after articles are packaged in cartons that are transported by the carrier chains. For example, if the support members tilt excessively, the walls of the cartons are caused to be slanted such that articles are not properly packaged in the carton, articles cannot fit through the opening of the carton, or the walls of the carton are not squared with respect to the support surface as the end flaps of the carton are folded and secured to form end walls.
According to one solution, to compensate for forces applied to a support member that would generate a large degree of tilt, a forward tilt is imposed upon the support member to compensate for the tendency of the support member to tilt rearwardly. Thereby, the displaced or tilted position of the support member generally squares the corners of the package pushing against it. However, the forward tilted support member does not square the corners of an unloaded carton since the unloaded carton generally does not produce as great of an opposing force against the support member as a package that is loaded with articles. As mentioned earlier, a non-square carton can lead to problems during loading. This is especially true for taller cartons where the upper and lower panels of the carton become more offset and can require remedies such as overhead squaring to be introduced into the process.
It is therefore desirable to limit the degree of differential tilt of the support members regardless of the magnitude of the opposing force exerted by either an unloaded carton or loaded package. This has been attempted using several methods. One method for decreasing differential tilt is to tightly control the distance, or play, between the surfaces of the chain guide track and the rollers of the carrier chain. This is expensive from a manufacturing standpoint since a guide track with tighter tolerances requires more precision to manufacture. Additionally, tighter tolerances cause increased contact and friction between the carrier chain and the guide track. As a consequence, the sprockets must supply a greater drive force, which in turn, causes the chain links and guide track to wear out faster. Another method is to increase the pitch of each individual attachment link. However, the pitch of the attachment link is dependent on the characteristics (diameter, spacing between teeth, and the like) of the sprocket that is selected to drive the other links of the carrier chain. Thus, the pitch of the attachment link can only exceed a standard chain link pitch by a limited amount if it is to be used with a sprocket that is designed for use with the standard chain link pitch.
Therefore, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies. What is needed is an improved carrier chain that reduces the undesirable differential tilt of an attached or integral support member in response to a force is applied to the support member. Further, the carrier chain should be easily manufactured and should have the ability to be incorporated into a standard roller chain.